The present invention relates to bolt assemblies used for locking and unlocking door-leaves or similar articles, and which comprise a bolt slidably housed inside a casing fixed on the inner face of the door-leaf, and movable from the outside by a key which is introduced into the barrel of a safety cylinder, the rotation of the barrel, after insertion of the key, being possible only if the latter is the key corresponding to the barrel, the movement being transmitted to the bolt through a tail-piece carried by the barrel.
In a known bolt assembly of this type, the safety cylinder, housed inside a passage extending through the door-leaf and whose end which is turned towards the outside, or outer end, projects relative to the door-leaf, is rigidly connected to the latter by two screws engaged in a plate placed between the inner or internal face of the door-leaf and the casing.
While benefiting from the security due to the safety cylinder, the fraudulent opening of a door provided with such a bolt assembly is not excluded when rotating directly the end of the cylinder which is protruding relative to the outer face of the door-leaf.